In U.S. Pat. No. 3,855,638 to Ontario Research Foundation, there are described surgical prosthetic devices and implants consisting of a metal substrate with a porous metal coating into which bone tissue may grow for incorporation of the prosthesis into the body. The porous metal coating comprises metal particles joined to each other and to the substrate to define a plurality of connected, interstitial pores uniformly distributed throughout the coating. The resulting porous coating is composed of regularly-shaped particles. The average interstitial pore size is at least about 50 microns to ensure bone tissue ingrowth for incorporation of the device into the body. The term "metal" as used therein (and also herein) refers to both pure metal and metal alloys.
As described in the earlier U.S. Patent, such composite articles may be formed by sintering procedures using metal particles of the required particle size, preferably about -100+325 mesh (about 50 to about 200 microns), the term "mesh" referring to the U.S. Standard Sieve mesh series.
Certain pure metals which otherwise are suitable for the formation of coatings on surgical prosthetic devices and implants are pyrophoric at very fine particle sizes. One such pure metal is titanium which is an attractive material of construction for a porous coating of a surgical prosthetic device or implant owing to its strength, inert character and light weight.